Students at the University of Sussex are holding a rally at its Brighton campus to protest against the proposed closure of the chemistry department.
Sussex University is renaming the department and cutting staff
The students blame financial mismanagement for the closure, claiming the institution has a £4m deficit.
But the university said the deficit was £2m and is unconnected to the changes.
"Basically, we have had too few students to support a viable chemistry department," said vice chancellor Professor Alasdair Smith.
"For the last five or so years we have been taking in about 20-25 students a year and that is simply not enough."
Second year chemistry student Natasha Gregory said students had chosen the university because it had one of the top chemistry departments in the country.
Many felt they would need to move to a different university to complete their courses if the department closed.
"Although Professor Smith has said that we could see out the rest of our degree here at Sussex, we cannot see how this would be possible," said Ms Gregory, from Leatherhead in Surrey.
The chemistry department, which is to be renamed chemical biology, would lose seven out of its 14 academic staff through voluntary redundancy.
Tuesday's rally aimed to raise awareness of the closure before the proposal goes before the senate, the university's governing body, on Friday.
The students have already collected more than 300 signatures against the plan and will raise a vote of no confidence in the management.
The university said its financial position was extremely tight, in common with many other further education institutions, and retaining the chemistry department would cost an extra £750,000.